Saturday, May 11, 2013

Charlotte's Web

One of the first stories of wildlife I remember reading was Charlotte's Web, by EB White. The unlikely friendship of a pig and a spider reassures the young reader that even when one thinks one is alone in the world, one really isn't.

Spoiler alert for those who haven't read the book, but enjoy reading books for youth and might one day read this one:

The story finishes with Wilbur, the pig, finding Charlotte, the spider, missing, and astonished that her offspring fly off into the wind with nary a concern for their future. With glee, they catch the wind with their threads, disappearing into the atmosphere.

Araneus Diadematus is Charlotte. She is the most abundant orb weaver in Canada who can claim responsibility for spiral (orb) webs larger than 30 cm.

Each day of their lives, as long as the weather is dry, they spend 30-60 minutes building a web in the dawn hours. Typically, they'll rebuild in the same location, but they will change locations to suit food abundance and personal safety. As they reach maturity, their mobility decreases (they are poor walkers) so they spend the final months of their lives in the same home, under a man-made ledge or a cluster of leaves in a hedge.

In the dark nights of fall, the now heavy females then make one final pilgrimage to find a nesting spot for their eggs.

October, 2012

She is gravid - her abdomen is full of eggs. After laying her eggs, her abdomen will shrink to about a fifth the size - the size of her cephalothorax (she will look similar to a male). She will guard her eggs, but ceasing to build any webs (a good nest site is not necessarily a good web site), will eventually starve and die.

On a spring day, about 6 months later (as was the case for these), the warmth and dryness will trigger her eggs to hatch. Thousands of tiny yellow bodies will cluster together for a few days while they get a bearing on life. Then one by one, they will crawl to a relatively high point where they will release a thread of silk, allowing it to be caught by the wind, and be ballooned off towards new lands.

Each one, with legs outspread, could fit inside the 'o' on your screen.

At least six eyes are visible.

Ballooning spiderlngs have been witnessed, kilometres-high in the sky. They are equivalent to atmospheric plankton, going where their currents take them. This effective dispersal strategy typically makes them the first arrivals to any newly terra-formed volcanic island, though they may need to wait a while for food to arrive.

As soon as they can walk, they know how to spin a web. Their instincts lead them to build their first web with a technique identical to the last web they will build. There are no practice webs, no "I was feeling lazy so this is the best I could do" webs, no bragging about "this is my best web, let me Facebook this". No emotional excuses for doing what they need to do to survive, to propagate their species. They build webs, simply because they are spiders.